The present invention relates generally to accurately detecting slow intrusion of moisture into sealed containers and more particularly relates to the detection of progressive moisture damage to the housed, hydroscopic, granular chemicals such as charcoal, silica gel, potassium superoxide and HOPCALITE.
The electrolytic moisture indicator provides an instantaneous and rapid check on the effectiveness of the seal imposed on the emergency breathing rescue devices, as well as on the remaining sorbent life in air charcoal filters and high-pressure drying cartridges.
Known related art includes U.S. Pat. No. 3,773,044 granted to Richard A. Wallace on Nov. 20, 1973 and British Pat. No. 445,457 granted 9/21/1934.
The British Pat. No. 445,457 uses a hydroscopic substance; e.g., alkaline iodide, which restricts placement of its moisture-responsive element in that a flowable gas or vapor must traverse the hydroscopic substance in order to render the moisture-responsive element effective.
Various emergency breathing rescue devices have been presented with the more prevalent being Oxygen KO.sub.2 SELF-RESCUERS, including the U.S. Bureau of Mines' combination 10 minute/60 minute breathing apparatus, Mine Safety Appliance's 60 minute self-breathing unit and Dragerwerk's oxygen self-rescuer device as well as filter self-rescuer containing HOPCALITE and charcoal. All self-contained oxygen breathing KO.sub.2 devices and filter self-rescuers must have a useful storage life of at least five years.
Repetitive cyclic maintenance is required to monitor a multiplicity of oxygen self-rescuer canisters in order to detect moisture intrusion through the mechanical or vacuum seal imposed on their metal or plastic external case. This is especially true in mines where canisters must be stored for five-year periods. Moisture reacts with the hydroscopic, moisture-sensitive, oxygen-producing chemical, e.g., potassium superoxide or HOPCALITE, contained within the canisters and, at a given level, moisture intrusion will render such devices ineffectual.
These canisters are subjected to very damp environments (such as in mines which may approach 100% relative humidity) and are subjected to severe mechanical abuses. For example, miners will use their mechanically rugged metal or plastic housing cases as a readily accessible hammer or tool. In addition, these oxygen self-rescuer devices are also shaken considerably. Such high impact abuses over several years tend to insiduously damage (create tiny holes) in the mechanical or vacuum-proofing seal used to protect the hydroscopic oxygen-generating and filter chemicals. Further, government regulations require that oxygen self-rescuer canisters be daily tested for leakage or moisture intrusion.
At present, inherent deficiencies exist with the mechanical and vacuum seals imposed on the emergency self-rescuer breathing units. For instance, in oxygen self-rescuers with a mechanical seal, e.g., MSA's 60-minute breathing unit, a critical problem occurs with the rubber (NEOPRENE-type) gasket forming the mechanical seal: Over long periods of usage up to five years and thereafter, aging of the NEOPRENE rubber under pressure takes place resulting in harmful increased moisture permeability (i.e., slow moisture intrusion) through the gasket. This gradually deactivates the chemical sorbent. This moisture intrusion accelerates in the presence of pinholes or rubber slits, not readily observable by the naked eye. Similarly, for the oxygen self-rescuer with a vacuum-imposed seal, e.g., Dragerwerk's breathing unit, the vacuum tends to lose its effectiveness during prolonged usage ranging from three to six years. As a result, gradual moisture intrusion occurs and is absorbed by the potassium superoxide chemical, thereby slowly and insidiously decreasing its oxygen-generating property.
The present electrolytic moisture indicator resolves this critical moisture intrusion problem into chemical canisters and air filters.